Digital clock

ABSTRACT

A digital clock is provided which includes a main shaft rotatably supporting a plurality of time indicating drums which have inner teeth on one side and driving teeth on the other side of their inner periphery. The clock also includes pinion locking means arranged within the time indicating drums on the same side as said driving teeth. A plurality of intermediate pinions are arranged within the drums to engage the pinion locking means and driving teeth on one side and with the inner teeth on the other side so that said drums are driven. One or two of the pinions consist of two parts which are slippable relative to each other by application of a predetermined torque therebetween for the purpose of time adjustment or day of week indication adjustment. A time mechanism installed in the clock includes a cam drum which is within a time setting drum.

United States Patent 191 Gate [451 Sept. 23, 1975 DIGITAL CLOCK PrimaryE.raminer--Joseph W. Hartary [75] Inventor: Kenjiro Goto, Tokyo, JapanAsslsmm Exammeriu' Weldon Attorney, Agent. or FtrmArmstrong, Nlkaido &[73) Assignee: Kansei Kogyo Kabushiki Kaisha, wegner Japan [22] Filed:Oct. 25, 1973 [57] ABSTRACT [21] L 409 4 9 A digital clock is providedwhich includes a main shaft rotatably supporting a plurality of timeindicating drums which have inner teeth on one side and driving [30]Forelgn Appllcatmn Pnomy Data teeth on the other side of their innerperiphery. The Nov. 9. 1972 Japan 47429308 lo k al o in lude pinionlocking means arranged within the time indicating drums on the same sideas l l 58/125 C; 5 26 E; 235/1 5 said driving teeth. A plurality ofintermediate pinions [5i] Int. Cl. Q0413 19/02 are arranged within thedrums to engage the pinion Field of Search 5 C, 2 1 6 16, locking meansand driving teeth on one side and with 58/19 R. l A, 21- 152 B; 235/115,1 R the inner teeth on the other side so that said drums are I driven.One or two of the pinions consist of two parts l References Cited whichare slippable relative to each other by applica- UNITED STATES PATENTStion of a predetermined torque therebetween for the 2.3-43,6i3 3/1944Goldsmith 58/125 c Purpose Of time adjustment or day of Week indication2 45 1/1949 Johnson h 58/126 E adjustment. A time mechanism installed inthe clock 2 734,333 2 95 Uhlig claim 53 125 C includes a cam drum whichis within a time setting 3.6l L705 l0/l97l Niznik...., 58/!25 C drum.3.7l2,050 1/1973 Kawada S /I25 C 12 Claims, 11 Drawing Figures US PatentSept. 23,1975 Sheet 1 of 3 FIG. 5

FIG.

PRIOR ART US Patent sfipt. 23,1975 Sheet 2 Of3 3,906,715

FIG. 5

FIG. 5

US Patent Sept. 23,1975 Sheet 3 of3 3,906,715

FIG. 8 FIG. 7

PRIOR ART FIG. 9

llil

DIGITAL CLOCK BACKGROUND OF THE INVENTION 1. Field of the Invention Thepresent invention relates to an improved digital clock mechanismincluding av timer for operating a switch, and an alarm.

2. Description of the Prior Art Heretofore, a clock mechanism has beendisclosed wherein a plurality of time indicating drums are mounted on amain shaft so that the drums may be driven intermittently through adouble-profile pinion which is mounted on another shaft outside of thetime indicating drums (U.S. Pat. No. 3,495,396). However, in such amechanism, mounting space required for the pinion and its shaft causesbulkiness of the clock and pinion clearing gap between the adjacent timeindicating drums, especially between the ten minute indicating drum andthe unit minute indicating drum, resulting in difficulty in readingtime.

Further, in a conventional digital clock, a time adjusting mechanismcomprises a particular clutch means arranged between a driving motor anda time indicating drum or between adjacent time indicating drums (U.S.Pat. No. 3,690,063). It has been found, however, that such a clutchmeans involvesa complicated structure. The structure is especiallydifficult to make using injection molding for the time indicating drumsof synthetic resin due to their complicated shape which is caused by theclutch means and a pinion gear disposed inside of the time indicatingdrums.

A conventional timer device used in a digital clock comprises a camdiskprovided with outer teeth for mating with a pinion gear which isdriven in unison with the time indicating drums. At least one lug isformed on the cam disk, and at least one cut out portion is formed ontime setting wheel whereby a timer switch is so arranged that the switchis operated when the lug on the cam disk enters into the correspondingcut out portion on the time setting wheel. However, such a timerconstruction requires not only considerable space in a digital clock butalso relatively complicated assembling process.

Further, in a conventional digital clock, a driving motor generallydrives directly a second indicating drum or a unit minute indicatingdrum which is disposed at right-hand side in a succession of. timeindicating drums. Therefore, a time adjusting wheel and/or a timeradjusting wheel are conventionally disposed separately from each otherresulting in difficulty in operation or complicated structure of theclock.

SUMMARY oF THE INVENTION Accordingly, one of the features of presentinvention is to provide an improved digital clock mechanism comprising aplurality of time indicating drums having inner peripheral teeth thedriving torque for which is transmitted through double-profile pinionsarranged inside of the time indicating drums. The pinions are carried onshafts fixed on plate members which are interposed between the adjacenttime indicating drums to be carried on a main shaft. Such pinions mayselectively comprise two parts which are resiliently coupled with eachother but slippable relative to each other by application of apredetermined torque for the purpose of time adjustment or day of weekindication adjustment.

Still another feature of the present invention is to provide an improvedtimer mechanism for use in a digital clock, comprising a time settingdrum carried on a shaft, a cam drum positioned within the time settingdrum carried on said shaft, inner teeth formed on the inner periphery ofthe cam drum, the inner teeth mated with a pinion which isdriven throughan idler gear by a driving shaft, a lug arranged on the cam drum, and acut out portion arranged on the time, setting drum, whereby a switchmeans, is operated when the lug enters into the cut out portion. I

Still another-feature of the present invention is to provide an easilyhandled adjusting mechanism for time indication and a timer setting in adigital clock wherein time indicating drums are carried rotatable arounda main shaft. A'time setting drum for a timer is fixed on the left endof the main shaft and a timer adjusting wheel is fixed to the right end.The unit minute indicating drum is fixed on the left end of a hollowouter shaft through which the main shaft extends and'a time adjustingwheelis fixed on the right end of the outer shaft adjacent to the timeradjusting wheel. Thus the two adjusting wheels are arranged adjacent toeach other at the right side of the clock.

Accordingly, it is a general object of the present invention-to providean improved digital clock mechanism overcoming.aforementioneddifficulties in conventional digital clocks. I

More specifically, it is an object of the present inven tion to providean improved driving mechanism in a digital clock to drive a successionofthe time indicating drums. 7

It is another object of the present invention to provide animprovedadjusting mechanism for time indication in a digitalclock.

It is'still another object of the present invention to provide animproved quick changer mechanism for day of week indication in a digitalclock.-

It is still another object of the present invention to provide animproved adjusting mechanism of easy adjusting of the time indicationand timer setting in a digital clock.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects, features and advantagesof the present invention will be apparent from the following descriptionof preferred. embodiment of the invention taken in connection with theaccompanying drawings forming a part thereof in which:

FIG. 1 is a fragmentary view partly in section showing a conventionaldriving mechanism in a digital clock.

FIG.,2 is an axial sectional view showing the improved driving mechanismand time adjusting mechanism of the invention. 7 j I FIG; 3 is anexploded perspective view showing a pair of adjacent timeindieatingdrums in FIG. 2.

. FIG. 4 is a front elevation partly in section showing an improvedarrangement of adjusting wheels for time indication and timer setting.

FIG. 5 is an enlarged sectional view showing a pinion in a modifiedembodiment accordingto the invention.

FIG. 6 is an enlarged sectional view showing a pinion of anotherembodiment.

FIG. 7 is an enlarged sectional view showing a pinion of still anotherembodiment.

FIG. 8-is an enlarged left side elevation in FIG. 7.

FIG. 9 is a fragmentary sectional view showing a conventional timermechanism for a digital clock.

FIG. 10 is a fragmentary sectional view showing an improved timermechanism in a digital clock according to the present invention.

FIG. 11 is a perspective view broken in part showing the timer mechanismin FIG. 10 mounted in a digital clock.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Now referring to FIG. I, thereis shown a conventional driving mechanism in a digital clock, wherein alower order time indicating drum 1 and an upper order time indicatingdrum 2 are mounted rotatably around a common main shaft 3 passingtherethrough. A double-profile pinion 4 rotatably supported on a pinionshaft 5 which is arranged outside of the time indicating drums l and 2is adapted to mate with outer driving teeth or lugs 6 on the lower orderdrum 1 and with outer peripheral teeth 9 on the upper order drum 2 sothat driving torque may be transmitted intermittently through the pinion4 between the adjacent drums.

Referring to FIGS. 2 and 3, there is shown an improved clock mechanismaccording to the present invention, wherein a second time indicatingdrum 11 is numbered on the outer periphery thereof from to 55 with fivegraduations therebetween, a unit minute indicating drum 12 is numberedon its outer periphery from 0 to 9, a ten minute indicating drum 13 isnumbered on its outer periphery in two repeating series of numbers from0 to an hour indicating drum 14 is numbered on its outer periphery from1" to 12", and a day of week indicating drum 15 is numb'ered on itsouter periphery from SUN.AM" to SAT.PM. A main shaft 10 extends througha pair of opposing walls of frame and rotatably supports thereon thesecond drum 11, the unit minute drum 12, the minute drum 13, and thehour drum 14 and the day of week drum 15. Between adjacent drumscircular support plates 16, 17, 18 and 19 are interposed and are piercedby the main shaft 10 and which support doubleprofile pinions 21, 22, 23,24, and 26 respectively thereon in such a manner that the pinions arearranged inside of the time indicating drums. The outer configuration ofthe support plates 16, 17, 18 and 19 are generally flush with theadjacent time indicating drums, but some lugs (not shown) maybe formedon the support plates for fixation onto frame 20.

An electric motor 27 is fixed on the frame 20 adjacently to the seconddrum 11 for supplying a driving torque to the second drum 11. A pinion29 carried on a driving shaft 28 of the motor 27 extends through thewall of the frame 20 to mate with inner teeth 31 formed on the innerface of a concentrically projecting wall 30 on the right side of thesecond drum 11. The teeth 31 mate with the pinion 29 on the motor andmay be formed on the outer side periphery of the second drum 11 becauseof the location of the motor and its driving shaft. On the innerperiphery at the left side of the second drum 11, there is provided apair of driving teeth and a pinion locking face 32.

The relation between the driving'teeth. a pinion locking face and adouble-profile pinion is described in connection with the unit minutedrum 12, ten minute drum 13 and double-profile pinion 23 as illustratedin FIG. 3. On the inner periphery at the left side of the unit minutedrum 12 there is provided a pair ofdriving teeth 40 and 41 and a pinionlocking face 33 which is a little shorter in the axial direction of thedrum 12 than the driving teeth 40 and 41. The support plate 17 has aneccentric recess 42. A shaft 43 rotatably carrying the double-profilepinion 23 passes through. This pinion is of the same type as a knowndouble-profile pinion for use in a digital counter and constructed suchthat the left-hand side thereof is 9-toothed, whereby the three teeth onthe lefthand side of the pinion 23 extend to form the three teeth on theright-hand-side thereof and the remaining teeth of the left-hand-sideare not extended. The pinion 23 is arranged on the shaft 43 in such amanner that the 3toothed side thereof protrudes through a cut outportion 44 of the recess 42 on the support plate 17 such that the3-toothed side mates with the driving teeth 40 and 41 and the pinionlocking face 33 on the' unit minute drum 12, wherein the six teeth onthe pinion 23 are short enough not to reach the locking face 33 but longenough to engage the pair of driving teeth 40 and 41 for smooth drivingof the pinion 23 by the driving teeth. The 9-toothed side of the pinion23 is adapted to engage the 36-toothed inner periphery 37 of the tenminute drum 13.

In operation, one revolution of the unit minute drum 12 causes the pairof driving teeth 40 and 41 thereon to advance only the three teeth onthe left-hand side of the double-profile pinion 23, and thereafter, thepinion locking face 33 of the drum 12 steps the rotating movement of thepinion 23 at its 3-toothed side until the pair of driving teeth 40 and41 mate again with the 3- toothed side. Therefore one revolution of theunit minute drum 12 causes l/12 of a revolution of the ten minute drum13.

In the substantially same manner as mentioned above, the pair of drivingteeth (not shown) and pinion locking face 32 on the second drum 11 areadapted to mate with the righthand side 21 of the double-profile pinion21 and 22, the lefthand side of which engages with 30-toothed innerperiphery 36 of unit minute drum 12. The pinion 21 and 22 is rotatablycarried on a shaft 45 on the support plate 16 and comprises two parts 21and 22 as described hereinafter. Diametrically opposed two pairs ofdriving teeth (not shown) and two pinion locking faces 34 on theleft-hand 'side of the ten minute drum 13 are adapted to mate with therighthand side of the double-profile pinion 24, the left-hand side ofwhich engages with 36-toothed inner periphery 38 of the hour drum 14.The pinion 24 is rotatably carried on a shaft 46 on the support plate18. A pair of driving teeth (not shown) and a pinion locking face 35 onthe left-hand side of the hour drum 14 are adapted to mate with theright-hand side 25 of the doubleprofile pinion 25 and 26 the left-handside of which engages with a 42 toothed inner periphery 39 of the day ofweek drum 15. The pinion 25 and 26 is rotatably carried on a shaft 47 onthe support plate 19 and comprises two parts 25 and 26 as describedbelow. All of the double-profile pinions 21, 22, 23, 24, 25 and 26 are3-toothed on the right-hand side and 9-toothed on the left-hand side.The support plate 16 or 18 between the drum 11 and unit minute drum 12or between the ten minute drum l3 and hour drum 14 is formed thickerthan the other support plates 17 and 19 so that adjacent drums l1 and 12or 13 and 14 may be clearly separated in location for easy reading ofthe time. For the same purpose, a colon mark (see FIG. 11) may beimpressed on the support plate 18. Further, a neon lamp (not shown) maybe installed at the inner hollow of the support plate 18 and/or 16 forilluminating the time indicating drums from the inside when the drumsare made of translucent or transparent material such as synthetic resin.

Thus one revolution of the second drum 11 causes 1/10 revolution of theunit minute drum 12, one revolution of which causes 1/12 revolution ofthe ten minute drum 13 as already described, one revolution of whichcauses 1/12 revolution of the hour drum 14, one revolution of whichcauses 1/14 revolution of the day of week drum 15, and as a result, eachdrum digitally indicates minutes, hours and day of week.

The double-profile pinion 21 and 22 between the second drum 11 and theunit minute drum 12 comprises two parts 21 and 22. One part 21 isprovided with a least one and at the most three projections 48 on itsside end facing the part 22 while the other part 22 is provided withthree recesses 49 on its side end facing the part 21 such that therecesses 49 may receive the projections 48. The two parts 21 and 22 areso arranged on the shaft 45 that the part 22 is biased toward the part21 by a coil spring 50 around the shaft 45, one end of which abutsagainst a washer-like retainer 51 fixed on the shaft 45 and the otherend of which pushes the part 22. These two parts are thus pressedagainst each other in engaged driving but slippable relation. The part22 is formed with a central recess to partially accommodate the spring50. The bushing 52 of the unit minute drum 12 is detachably fixed on anend of a first outer shaft 53 through wich the main shaft rotatablyextends. A time adjusting wheel 54 is fixed on the other end of theouter shaft 53 (see FIG. 4) to operate the unit minute drum 12.

In operation, the time adjusting wheel 54 rotates,-

through the first outer shaft 53, the unit minute drum 12 which isrotatable together with the left-hand part 22 of the double-profilepinion since the part 22 is rotatably slippable against the pressingforce of the spring 50 relative to the part 21 which is stopped by thepinion locking face 32 on the second drum 11. Thus the indicated time isadjustable by revolution of the time adjusting wheel 54 which istransmitted incrementally to the unit minute drum 12, the ten minutedrum 13, the hour drum 14, and finally the day of week drum 15.

FIG. 5 illustrates another embodiment of the doubleprofile slippablepinion of the type described above, wherein a first part 59 is providedon one end facing a second part 60 with plural projections 61 and 62. Acentral bushing 63 is formed thereon with an enlarged head 64 and withone or more slits 65 such that the central bushing 63 may bearresiliency in the diametrical direction of the bushing which will permitthe second part 60 to fit onto the central bushing 63 over the enlargedhead 64. The central bushing 63 extends beyond the second part 60. Thesecond part 60 may be slid when the double-profile slippable pinion isin an operative condition. A coil spring 66 is positioned between thesecond part 60 and an E ring 67 supported on the head 64 of the centralbushing 63 so that the second part 60 is held against the first part 59whereby recesses 68 and 69 on the second part, facing the first part 59,receive the corresponding projections 61 and 62.

FIG. 6 illustrates still another embodiment of the double-profileslippable pinion wherein a first part 70 is provided with a centralbushing 71 on the outer end of which is formed plural circumferentialrecesses 72 and 73. The recesses 72 and 73 are adapted to receivecorresponding projections 74 and 75 formed on plural resilient tongues76 and 77 which extend from a second part 78 around the central bushing71 of the first part 70. Thus the second part 78 is rotatable byapplication of a predetermined torque thereon relative to the first partwhereby the projection on the resilient tongue 77 is positioned in theadjacent recess (not shown) on the central bushing 71. The centralbushing 71 may be formed with an extension (not shown) beyond theresilient tongues 76 and 77 so that a washer like retainer (not shown)may be fixed on the extension to prevent the second part 78 fromdisengaging the central bushing 71.

FIGS. 7 and 8 illustrate still another embodiment of the double-profilepinion wherein a first part 79 is provided with a central bushing 80 ofsquare cross section which is received within a cylindrical inner space81 of a second part 82. The circumferential face of the central bushing80 abuts against an arcuated leaf spring 83 both ends of which aresupported on step portions 84 and 85 on the inner periphery of thesecond part 82, to control the intermittent revolutions of the bushing80. The second part 82 is rotatable by a predetermined torque relativeto the first.part 79 with the leaf spring 83 moving over the corneredges 86 of the central bushing 80.

The double-profile pinions shown in FIGS. 5 to 8 are as seen from thedrawings 4-to'othed on the right side and 8-toothed on the left side. Itis to be understood that the number of teeth on each side of the pinioncan be altered for the purpose of the present invention and within thescope of the invention. It is also advantageous to make the pinions ofsynthetic resin.

FIG. 9 shows a conventional timer mechanism for a digital clock, whereina time setting drum 87 is rotatably carried on a shaft 86. The side faceof the drum has one or more recesses or cut out portions 89 which areadapted to accommodate corresponding projections 90 and 91 formed on aside end of a cam disk 92 rotatably carried on the shaft 86 and arrangedoutside of the time setting drum 87. Circumferential gear 93 on the camdisk 92 mates with-a pinion 94 driven by, for instance, a drum such asthe drum shown in FIG. 1 so that the cam disk 92 may be rotated to movethe projections 90 and 91 thereon'into the corresponding recesses 89 onthe time setting drum 87. The cam disk 92 is thus pushed toward the timesetting drum 87 by a plate 95 biased by spring 96, and thus a switch 97is operated. 9

Referring to FIGS. 4, l0 & 11,. a timer mechanism according to thepresent invention is shown wherein a time setting drum 98 is fixed onthe main shaft 10. The drum 98 accommodates a cam drum 102 of smallerdiameter in such a manner that the cam drum 102 is rotatable around abushing 103 of the time setting drum 98. The drum 102 is biased axiallytoward the time setting drum 98 by a spring 104 interposed between thedrum 102 and a washer-like retainer 105 fixed on the outer end of thebushing 103. The cam drum 102 is provided with one or more projections100 and 101 which are adapted to be received, when the timer isactuated, within corresponding slots or cut out portions 99 formed onthe time setting drum 98. The time setting drum 98 is biased togetherwith the cam drum 102 by a spring disposed between the frame 20 and thetime setting drum 98 toward the time indicating drum so that the extremeend of the bushing 103 abuts the side face of a pinion 109 on the secondoute'r shaft 110.-

A reduction gear 107 is rotatably carried around a shaft 108 on theframe 20. The reduction gear comprises a pinion side 107b to gear withinner peripheral teeth 106 on the cam drum 102 and a wheel side 107A tomate with the pinion 109 at one end of the second outer shaft 110disposed around the main shaft 10. The pinion 109 is formed integrallyon one end ofthe second outer shaft ll to transmit therotationalmovement of the ten minute drum'13. The minute drum 13 is indetachablyfixed relation with the other end of the second outer shaft 110 (seeFIG. 2 or 4).

A switch 111 such as a microswitch is arranged on the frame to beoperated by-horizontal axial movement of the cam drum 102 around thebushing 103 of the time setting drum 98. The projections 100 and 101 onthe cam drum 102 are adapted to separate the drum 102 from the timesetting drum 98 in the inoperative position of the timer, and are soarranged at radially different positions on the side face of the cam 102that the projections enter into the correspondingly disposed slots 99 onthe time setting drum 98 only one time each revolution of the cam drum102. Thus one complete revolution of the cam drum 102 causes oneoperation of the switch 111. v

The time setting drum 98 is numbered at its outer periphery from 1 to 12or 24 andis formed at the peripheral side portion with ratchet gears 113mated with a spring biased pawl 114 carried around a shaft 115 on theframe 20. Thus the time setting drum 98 rests in the respective settingposition and may be rotatable in one direction to protect othermechanisms in the digital clock. The time settingdrum'98 is adjustablefrom the outside through thesmain shaft 10. The main shaft 10 fixedlysupports on oneend the time setting frum 98 and fixedly supports on theother end a'timer adjusting'wheel 112 adjacent to and outside'of thetime adjusting wheel 54 at the righthand side of the digital clock asshown in FIG. 4.

The present invention may be embodied in other specific forms withoutdeparting from the spirit or essential characteristics thereof. Thepresently disclosed embodiments are therefore to be considered in allrespects as illustrative and not restrictive, the scope of the inventionbeing indicated by the appended claims rather than the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraces.

ranged inside each of said time indicating drums drums rotatably andadapted to engage said inner teeth on one side and said driving teeth onthe other side thereof so as to transmit the driving force from saidlowest order time indicating drum to the upper order time indicatingdrums;

a plurality of pinion support plates positioned between each of saidtime indicating drums each pinion support plate having a cut out, acover, parallel to said pinion supported plate which covers one part ofsaid cut out;

a pinion shaft fixedly arranged through said cut out to rotatablysupport each said pinion thereon; and

a pinion locking means arranged on said other side of the inner lockingmeans arranged on said other side of the inner periphery of said drumsand adapted to engage said intermediate pinions on said other sidethereof to prevent rotational movement of said intermediate pinionswhereby the driving force exerted on said lowest order time indicatingdrum from said driving source is transmitted intermittently to each ofsaid upper order time indicating drums.

2. A digital clock as set forth in claim 1, wherein said main shaftpasses through said pinion support plates and wherein said pinion shaftis fixed to said cover at one end thereof.

3. A digital clock as set forth in claim 2, wherein said cut outincludes said covered portion and an uncovered portion and wherein saiduncovered portion is positioned on said support plate such that saidpinion on said pinion shaft engages said driving teeth and said pinionlocking means of the adjacent time indicating drums.

4. A digital clock as set forth in claim 3, wherein the outer peripheryof each said pinion support plate is generally flush with the outerperipheries of the adjacent time indicating-drums.

5. A digital clock as set forth in claim 1, wherein said coupling meansincludes a driving pinion and a driving shaft of said driving sourceadapted to carry said driving pinion and wherein said driving pinionengages the inner teeth on said lowest order time indicating drum so asto supply the driving force from said driving source to said lowestorder time indicating drum.

6. A digital clock as set forth in claim 1, wherein at least one of saidintermediate pinions includes first and second means rotatably carriedaround said pinion shaft one of which is provided with a projection andthe other of which is provided with a recess adapted to receive saidprojection and wherein said projection and said recess are normallyresiliently biased against each other by resilient means whereby saidfirst and second means of said pinion are slippable relative to eachother by application of a predetermined torque therebetween.

7. A digital clock as set forth in claim 6, wherein said first means ofsaid slippable pinion is provided with a central bushing around whichsaid second means of said slippable pinion is rotatably carried wherebysaid bushing extends beyond said second means and wherein a spring ispositioned between the outer end of said bushing and said second meanswhereby said second means is biased resiliently toward said first means.

8. A digital clock as set forth in claim 7, wherein said first means ofsaid slippable pinion is provided with a central bushing around whichsaid second means of said slippable pinion is carried wherein saidsecond means includes an axial resilient extension extending coaxiallywith said bushing whereby said projection formed on either said bushingor extension is received in one of said recesses formed on one ofthebushing or extension.

9. A digital clock as set forth in claim 8, wherein said first means ofsaid slippable pinion includes a central bushing of polygonal crosssection around which said second means of said slippable pinion isrotatably carried and said second means includes at the inside thereof aresilient member adapted to abut said bushing.

10. A digital clock as set forth in claim 9, wherein the other endthereof.

1. A digital clock comprising: a frame means; a main shaft supported onsaid frame means; a driving source; A plurality of time indicating drumsrotatably mounted on said main shaft each time indicating drum includinginner teeth on one side and driving teeth on the other side of the innerperiphery thereof; coupling means for coupling said driving source tothe lowest order time indicating drum and for transmitting a drivingforce from said driving source to the lowest order time indicating drum;a plurality of intermediate pinions respectively arranged inside each ofsaid time indicating drums and adapted to engage said inner teeth on oneside and said driving teeth on the other side thereof so as to transmitthe driving force from said lowest order time indicating drum to theupper order time indicating drums; a plurality of pinion support platespositioned between each of said time indicating drums each pinionsupport plate having a cut out, a cover, parallel to said pinionsupported plate which covers one part of said cut out; a pinion shaftfixedly arranged through said cut out to rotatably support each saidpinion thereon; and a pinion locking means arranged on said other sideof the inner locking means arranged on said other side of the innerperiphery of said drums and adapted to engage said intermediate pinionson said other side thereof to prevent rotational movement of saidintermediate pinions whereby the driving force exerted on said lowestorder time indicating drum from said driving source is transmittedintermittently to each of said upper order time indicating drums.
 2. Adigital clock as set forth in claim 1, wherein said main shaft passesthrough said pinion support plates and wherein said pinion shaft isfixed to said cover at one end thereof.
 3. A digital clock as set forthin claim 2, wherein said cut out includes said covered portion and anuncovered portion and wherein said uncovered portion is positioned onsaid support plate such that said pinion on said pinion shaft engagessaid driving teeth and said pinion locking means of the adjacent timeindicating drums.
 4. A digital clock as set forth in claim 3, whereinthe outer periphery of each said pinion support plate is generally flushwith the outer peripheries of the adjacent time indicating drums.
 5. Adigital clock as set forth in claim 1, wherein said coupling meansincludes a driving pinion and a driving shaft of said driving sourceadapted to carry said driving pinion and wherein said driving pinionengages the inner teeth on said lowest order time indicating drum so asto supply the driving force from said driving source to said lowestorder time indicating drum.
 6. A digital clock as set forth in claim 1,wherein at least one of said intermediate pinions includes first andsecond means rotatably carried around said pinion shaft one of which isprovided with a projection and the other of which is provided with arecess adapted to receive said projection and wherein said projectionand said recess are normally resiliently biased against each other byresilient means whereby said first and second means of said pinion areslippable relative to each other by application of a predeterminedtorque therebetween.
 7. A digital clock as set forth in claim 6, whereinsaid first means of said slippable pinion is provided with a centralbushing around which said second means of said slippable pinion isrotatably carried whereby said bushing extends beyond said second meansand wherein a spring is positioned between the outer end of said bushingand said second means whereby said second means is biased resilientlytoward said first means.
 8. A digital clock as set forth in claim 7,wherein said first means of said slippable pinion is provided with acentral bushing around which said second means of said slippable pinionis carried wherein said second means includes an axial resilientextension extending coaxially with said bushing whereby said projectionformed on either said bushing or extension is received in one of saidrecesses formed on one of the bushing or extension.
 9. A digital clockas set forth in claim 8, wherein said first means of said slippablepinion includes a central bushing of polygonal cross section aroundwhich said second means of said slippable pinion is rotatably carriedand said second means includes at the inside thereof a resilient memberadapted to abut said bushing.
 10. A digital clock as set forth in claim9, wherein said resilient member is an arcuated leaf spring which isfixed in an inner space formed in said second means.
 11. A digital clockas set forth in claim 6, wherein said slippable pinion is arrangedbetween a second indicating drum and a unit minute indicating drum. 12.A digital clock as set forth in claim 11, wherein an outer shaft isrotatably arranged around said main shaft supporting said plurality oftime indicating drums, and wherein said outer shaft engages a unitminute indicating drum at one end and a time adjusting wheel at theother end thereof.